Its fairly obvious that the cost of living in Silicon Valley requires an average salary much higher than Chicago. There is also the issue of having fairly well developed engineering programs at the other schools which also tend to demand much higher average salaries. So the comparison with those schools is skewed. You might just want to look at UChicago vs Pomona which have similar major offerings. Finally I never have been a big fan of average salaries per school, so much is dependent on major and the location where the job is (they are not normalized for these factors). The fact that a lot of students remain local should show Stanford engineering grads with the highest wages (along with the highest cost of living) which it does.